Process and apparatus for recovery of precious metals



Apr. 10, 1923. 1,451,454

F. A. BEAUCHAMP PROCESS AND APPARATUS FOR RECOVERY OF PRECIOUS METALSFiied Au 4, 1920.

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Be it known that l, Ennunmcn A. BEAU- cHAMr, a British subject, residingat Berkeley in the county of Alameda and State of Ca 'fornia, haveinvented a new and useful Improvement in Process and Apparatus forRecovery of Precious Metdls, of which the following is a specification.

. This invention.relatestor the i'gover'y of precious metalsbyamalgamation witli'mw he invention includes a novel recess and mium andwhat is known as rusty or coated gold, all of which are not amalgamableby simple contact with a pure mercury surface.

Althou h there are on record a few instances w ere the ore has beenmilled in a solution of cyanide and then successfully treated by! theamalgamation process consisting of passing the pulp of ground ore and canide solutlon over amalgamated copper plates in the usual way, yet inmost instances it has been found that unless very dilute cyanidesolutions'are used in the rocess the amalgam on the plates is attacke bythe cyanide solution, the gold being apparently dissolved and themercury running ofi, leaving the plates bare, and thus rendering furtheramalgamation impossible. Even where a satisfactory amalgamation has beenrecorded as having been made in this way yet the copper plates have beenfound to be afiacked through the coating of amalgam, necessitating theirfrequent renewal.

Now it is in the case of most ores a desirable procedure to mill in acyanide solution and in the case of many ores, especially thosecontaining coarse free gold and metallic silver, it would be beneficialto remove such coarse and freemetal by amalgamation prior to the usualmethods of cyanide treatment and it is to render such a combinationfeasible and possible whenever 'so desired OF BERKELEY, CALIFORNIA.

were.

1920. Serial $6. $01,168.

that I have developed the machine hereinafter to be described.

my invention I produce a surface of flu1 mercury that is maintained atany angle from the horizontal that may be desired b adjusting the speedof rotation, and the pu p of ground ore and solution is kept movlng overits, surface by the hydrostatic chine ;the particles of V precious metalbeing heavier than the gangue are projected by the centrifugal forcetowards the surface of the mercury wherewith they amalgamate as soon ascontact with the surface is established. A w

With particular reference to the accompanying drawing, the machine thereshown is especially designed to overcome various head given to the pulpentering the maobjections in the application of the principle 7 ofamalgamation by sodium amalgam in the treatment of platinum, rus gold,etc. The machine comprises a how 10 having a smooth inner surface. Thisbowl is carried by a vertical shaft .11 which is supported by bearings12. The shaft and bowl are rotated by means of bevel gears 13 which aredriven by a horizontal shaft 164. The bowl is formed with an inwardlyprojecting lip 15 at its upper end and a curved rim or hp 16 terminatingabove a discharge launder 17.

I A cylindrical feed spout 18 is supported on a frame 19 and extendsinto the bowl to a point short of the bottom thereof where it ispreferably provided with a constricted neck 18". A dynamo or generator27 is operated by the driving shaft 14. This nerator is electricallyconnected to the cy der 18by a connection 28 and with the bowl 958 10 bya connection'29. The cylinder 18 con-. stitntes the anode and the bowlthe cathode. A mercury layer or film 20 is built up along the walls ofthe bowl to seal the bottom of the feed spout.

In the operation of the device, sufiicient mercury is introduced intothe bowl to create a film as shown at 20 and pulp is fed into thecylinder 18. Since the cylinder extends downwardly into the film ofmercury and has its exit .closed thereby, the efiect is to force thepulp through the mercury by means of hydrostatic head built up in thecylinder 18. This brings) the particles of the precious. metal into moreintimate contact with the mercury than would otherwise occur. The pulphaving passed over themercury surprecious metal therein, is dischargedover the top of the bowl and enters the discharge launder 17 from whichany particles of precious metal that may have escaped amalgamation canbe recovered.

The most important result efiected by the machine above described is theprovision of a fluid bed or film of mercury that is independent of thesupport of a plate of metal capable of being amalgamated or wetted byit, as. in the case of the ordinary amalgamated copper plate. Theadvantage of this is that the gold and silver amalgam formed remainsfluid instead of becoming pasty or even hard as on a copper plate, andtherefore the old and silver contained therein are hardly appreciablyaffected by the dissolving action of the cyanide solution;v neither hasthe mercur any supporting metal that can be attacke by the saidsolution. The difiiculty of applying such a principle without the use ofa machine of the type specified in my invention lies in the fact thatmercury in the fluid state naturally assumes the horlzontal position,and an inclined plane surface cannot be produced, and if ore pulp werepassed over such a horizontal bath of fluid mercury at the proper speedfor amalgamation, the coarser particles would settle thereon and silt upthe surface rendering further amalgamation impossible.

It has long been known that metals such as platinum, osmiridium' andrusty gold through not amalgamable by contact with mercury alone areeasily wetted and held by mercury in which metallic sodium has beendissolved, or in other words by sodium amalgam. It usually happens insuch cases, however, that as soon as the sodium has been abstracted fromthe mercury by combination with the water in the ore-pullo, according tothe reaction Na+H,O= aOH-i-H the mercury ceases to hold the particles ofprecious metals, which as soon as the film of mercury recedes from themare free to be carried away with the gangue by the flow of pulp. It isthus important that if the precious metal particles are to be kept wet ythe mercury andthereby kept entangled by it and retained while thegangue flows away, a continual supply of metallic sodium mustbemaintained in the bath of mercury. This can best be accomplished bydissolving a sodium salt such as sodium chloride or sodium hydroxide inthe water used to suspend the crushed ore, and by means of an electriccurrent electrolyzing the sodium salt, continually depositing metallicsodium on the mercury Whlch is made the cathode 7 of the system.

The difiiculty heretofore experienced int applying this principle inpractice has lain in the fact that if an inclined amalgamated copperplate be used and the. pulp allowed actress to flow over it, thethickness of the film of electrolyte is not sufficient to make itpossible to have an anode in contact with theelectrolyte without its.formin an electrical contact with the cathode %in this case theamalgamated copper plate) and thereby short circuiting the current andmaking electrolysis impossible. There have been various schemessuggested to obviate this difiiculty. One such scheme is to have anincline plane of wood or other suitable material wherein transversegrooves or rifiies are constructed and filled with mercury; the pulp, asit passes over these rifiies is intended to be raised to such athickness as to admit of the placing of an anode in contact with it andyet suficiently far from the mercury surface or cathode as'to allow ofthe electrolysis .of the electrolyte without danger of contact with thecathode and consequent short-circuiting of the current. This scheme,

however, has not proven successful in practice.

In order to obviate the above difiiculties, there has been suggested amachine consisting of a slowing revolving horizontal cylinder lined withanamalgamable metal, e. copper, at a suitable distance from whic allaround the periphery, are placed horizontal bars of some conductingsubstance (such as iron or carbon) to act as anodes. The ground ore in amedium of solution of sodium salt is run through the cylinder, thesolution being simultaneously electrolyzed by the current and sodiumdeposited on the amal amated copper surface, thereby causing t eparticles of recious metal to adhere thereto and thus come separatedfrom the gangue. The dificulty with this apparatus has been found to bethat owin to the depth'of the bed of pulp passing t rough the machine,coupled with the agltation action produced b the revolution of the clinder, only the arger and heavier particles of precious metal can comein contact with the mercury surface and become entangled thereon, thelighter particles remaining in suspension in the electrolyte and beingcarried out with the tailing.

It will be seen from the foregoing that I produce an inclined surface ofmercu at any angle from the horizontal that may be desired, by adjustinthe speed of rotation of the machine. T e pulp in a medium of watercontaining a salt of sodium in solution passes between the mercurysurface and the anode, during 'which period by the action of thecurrent, sodium is deposited from the electrolyte on the mercury surfaceforming sodium amal am, while simultaneously the precious meta particlesare, by the action of centrifugal force, carried towards the surface ofthe sodium amalgam where they are at once caught and held as soon ascontact is established.

over the top, thus preventing The hydrostatic head under which the pulpenters the machine keeps the 'gangue particles in the pulp continuallymoving ing shows an apparent contact between the bottom edge of theanode and the mercury cathode but this contactis ma'd ejby an ex.-

@ tensionof non-conducting material 30 such as hard rubber or bakehte,so as to avoid electrical contact between the two electrodes.

This shape of the neck, althoughnot an es- 'sential part of theinvention, has been found toenhance the effect in certain cases, since,

it thus ensures aniore intimate contact between theore particles and thesodium g m V,

I claim. and desire to secure by Letters Pat'- ent is-' 1. A machine forthe recovery of precious 4 metals by amalgamation with mercury,comprising a centrifugal bowl so shaped as to confine'a layer of fluidmercury around Having thus described my ii it'figwma walls at an angleto the horizontal, a feed spout for the pulp extending downwardly intothe bowl and sealed at its lower end by the mercury, the lower portionof said fegilspout being formed of insulating mate- 11 v a 2. A machinefor the reccvery of precious metal by amalgamation with mercury,comprising a rotatable bowl shaped to confine a layer of fluid mercuryaround its walls by centrifugal action when rotating," a feed spoutextending downwardly into the bowl, the lower end of said spout beingformed of insulating material and adapted to'be sealed by the mercury,an electrical connection for the feed spout constituting the anode, andan electrical connection for'the bowl constituting the cathode fordirecting electrical current through the pulp.

my. hand in the presence of two subscribing -witnes.Ses.

' FREDERICK A. BEAUCHAMP. Witnesses:

' W. W. Emmy, M. E. Ewmc.

InTestimony whereef I havehereuntosi

